The present invention relates to an improved steerable electrode catheter having an irrigated tip that is particularly useful for treating atrial fibrillation.
Atrial fibrillation is a common sustained cardiac arrhythmia and a major cause of stroke. This condition is perpetuated by reentrant wavelets propagating in an abnormal atrial-tissue substrate. Various approaches have been developed to interrupt wavelets, including surgical or catheter-mediated atriotomy. It is believed that to treat atrial fibrillation by radio-frequency ablation using a catheter, continuous linear lesions must be formed to segment the heart tissue. By segmenting the heart tissue, no electrical activity can be transmitted from one segment to another. Preferably, the segments are made too small to be able to sustain the fibrillatory process. A preferred technique for treating atrial fibrillation by radio-frequency ablation would be a xe2x80x9cbranding ironxe2x80x9d approach, where a relatively long electrode can be held stationary in good contact with the heart wall while ablation is completed. In this way, a continuous transmural burn may be effected.
U.S. Pat. No. 5,800,428 to Nelson et al. discloses a radio frequency ablation catheter system having a flexible, tubular electrode for creating a continuous linear lesion. The tubular electrode is selectively extendable from the distal end of the catheter. The catheter further comprises mechanisms for remotely manipulating and extending the electrode. However, having an extendable electrode house in the catheter provides less degrees of freedom with respect to the shape, size and length of the tubular electrode. Moreover, the physician has to deal with additional moving and manipulatable parts, adding complexity to the procedure. Further, a retractable electrode can cause contamination because blood or coagulate on the electrode can be pulled into and entrapped inside the catheter. The entrapped coagulate can also affect the ability of the electrode to be further extended and retracted. Accordingly, it would be desirable to provide a catheter design having an electrode for creating linear lesions that overcomes these drawbacks.
The present invention is directed to a catheter having a non-retractable xe2x80x9cbranding ironxe2x80x9d electrode. In one embodiment, the invention is directed to a catheter for-ablating tissue comprising a catheter body, a tip section, a branding iron assembly, and a means for introducing fluid into the tubular electrode. The catheter body has an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The tip section comprises a segment of flexible tubing having proximal and distal ends and at least one lumen therethrough. The proximal end of the tip section is fixedly attached to the distal end of the catheter body. The branding iron assembly has proximal and distal ends and is fixedly attached at its proximal end to the distal end of the tubing of the tip section. The branding iron assembly is bent relative to the tubing and comprises a non-retractable tubular electrode formed of a material having shape-memory having at least one irrigation port through which fluid can pass from the inside to the outside of the electrode. A preferred means for introducing fluid comprises an infusion tube extending through a lumen in the tip section and having proximal and distal ends. The distal end of the infusion tube is in fluid communication with the proximal end of the tubular electrode. The tubular electrode of the invention acts as a branding iron, forcing tissue out of shape. This design produces more pressure on the tissue than a traditional catheter tip comprising a flexible plastic tubing with a series of ring electrodes mounted thereon.
In another embodiment, the invention is directed to a method for treating atrial fibrillation. According to the method, the distal end of a catheter as described above is inserted into an atria of the heart. At least one linear lesion is then formed in the atrial tissue with the tubular electrode.
In another embodiment, the invention is directed to a method for treating atrial fibrillation comprising providing a catheter as described above and a guiding sheath having proximal and distal ends. The guiding sheath is introduced into the body so that the distal end of the guiding sheath is in an atria of the heart. The catheter is then inserted into the proximal end of the guiding sheath and fed through the guiding sheath so that the distal end of the catheter extends out the distal end of the guiding sheath. At least one linear lesion is then formed in the atrial tissue with the tubular electrode.
In still another embodiment, the invention is directed to a method for treating atrial fibrillation similar to as described above. The catheter comprises a branding iron assembly that is generally L-shaped. The at least one linear lesion is formed in an open region of the heart with the tubular electrode.
In yet another embodiment, the invention is directed to a method for treating atrial fibrillation similar to as described above. The catheter comprises a branding iron assembly that is generally lasso-shaped. The at least one linear lesion is formed in or around a blood vessel with the tubular electrode.
In still yet another embodiment, the invention is directed to a method for treating atrial fibrillation similar to as described above. The branding iron assembly further includes an atraumatic tip comprising a coil spring, which is mounted at the distal end of the assembly.